This project will develop Diagnostics For Biodefense against Lassa fever, a severe, often fatal viral hemorrhagic fever (VHF). Because of its high case fatality rate, ability to spread easily by human-human contact, and potential for aerosol release, Lassa virus (LASV), the causative agent of Lassa fever, is classified as a Biosafety Level 4 and NIAID Biodefense category A agent. Our team has successfully produced prototype LASV enzyme-linked immunosorbent assays (ELISA) that are based on recombinant proteins rather than on reagents that must be produced in high containment laboratories. We have also newly established a research program in Sierra Leone, an area endemic for LASV, that provides unique clinical and laboratory resources for VHF research. We will now perform critical steps in the preclinical development of commercial recombinant antigen Lassa fever diagnostics. In MILESTONE 1 we will development commercial Lassa fever recombinant antigen-capture and immunoglobulin M (IgM) and immunoglobulin G (IgG) antibody-capture ELISA using a Performance Panel of well-characterized sera. In MILESTONE 2 we will development Lassa fever recombinant lateral flow point-of-care diagnostics. In MILESTONE 3 we will convert to manufacturing recombinant ELISA and lateral flow assays under Good Manufacturing Practices (GMP) with Quality Assurance (QA)/Quality Control (QC) to provide quantities of commercial grade diagnostic kits sufficient for preclinical evaluation of design control parameters to achieve benchmarks required for FDA approval. In MILESTONE 4 we will optimize scale up/purification of recombinant LASV proteins, GP1, GP2, and NP and monoclonal antibodies (mAbs) to recombinant LASV GP1, GP2, and NP. We will also convert to manufacturing with QA/QC, to provide quantities of recombinant proteins and mAbs sufficient for development and testing of commercial assays. In MILESTONE 5 we will define and collect positive and negative sera for assay validation from diverse regions across the Lassa fever endemic range of West Africa and elsewhere. These sera will be used to test and compare the commercial LASV recombinant ELISA and recombinant lateral flow point-of-care diagnostic assays with results from BSL-4 ELISA and PCR assays. RELEVANCE (See instructions): The potential use of LASV as a biological weapon necessitates development of methods to diagnose individuals exposed to and/or infected with LASV. The impact of Lassa fever in endemic areas of West Africa is immense, and a safe and effective diagnostic can also provide a very significant public health benefit.